1. Field of the Invention
The present invention in the field of biochemistry and medicine is directed to angiogenesis-inhibitory polypeptides comprising a part of human kininogen, particularly, the D3 domain (HK-D3) and variants thereof, and their use in diagnosis and therapy of diseases associated with endothelial cell migration and proliferation. In particular these polypeptides are useful in treating subjects with cancer.
2. Description of the Background Art
Angiogenesis, the formation of new capillaries form pre-existing ones (Folkman, J., N. Engl. J. Med., 1971, 285:1182–1186; Hanahan D. et al., Cell, 1996, 86:353–364), is a normal part of embryonic development, wound healing and female reproductive function. However, angiogenesis also plays a pathogenic role in the establishment and progression of certain diseases. Cancer, rheumatoid arthritis and diabetic retinopathy are examples of such diseases (Carmeliet P. et al., Nature, 2000,407:249–257). Anti-angiogenic therapy holds promise in inhibiting the progression of these diseases.
Angiogenesis can be triggered by several pro-angiogenic cytokines. In the setting of cancer, tumor cells under hypoxic conditions secrete vascular endothelial growth factor (VEGF) and/or fibroblast growth factor (bFGF). These proteins diffuse and bind to specific receptors on endothelial cells (ECs) in the local vasculature, perturbing the balance of pro- and anti-angiogenic forces in favor of angiogenesis. As a consequence of binding these proteins, ECs are activated to (a) secrete enzymes that induce remodeling of the associated tissue matrix, and (b) change the patterns and levels of expression of adhesion molecules such as integrins. Following matrix degradation, ECs proliferate and migrate toward the hypoxic tumor, resulting in the generation and maturation of new blood vessels.
Interestingly, many anti-angiogenic factors result from the degradation of matrix proteins—i.e., are a result of the action of pro-angiogenic enzymes. Examples include endostatin, a fragment of collagen XIII (O'Reilly, M. S. et al., Cell 1997, 88:277–285); kringle 5 of plasminogen (O'Reilly, M. S. et al., Cell, 994, 79:315–328) and PEX, the C-terminus non-catalytic subunit of MMP-2 (Brooks P C et al., Cell, 1998, 92:391–400).
The concept has emerged that, due to the abundance of pro-angiogenic factors, these anti-angiogenic molecules are unable to overcome the pro-angiogenic balance in a primary tumor. However, since they are secreted into circulation, these anti-angiogenic molecules are capable of inhibiting angiogenesis at other locations where tumor cells may have begun to invade. Consequently, micro-metastases comprising these tumor cells at these new locations remain dormant. This hypothesis explains the puzzling observation made by surgeons many years ago: at various times after surgical removal of a primary tumor in a patient with no obvious metastatic disease, the patient returns with advanced metastatic disease.
Thus, clinical intervention by treatment with one or more of the anti-angiogenic factors could inhibit the angiogenic process and halt tumor growth as well as metastasis. Significant evidence in the literature (cited above) supports this notion.